DDW-2024-011485

Estimate Disinfection CT & Whether Meeting 4-Log Virus Inactivation
Estimate Pipe Volume V=L*Pi*(R)2
Pipe Description Length (ft)Diameter
(inches)
Diameter
(feet)Volume (ft3)Volume (gal)% Full Effective Water
Volume (gal)
CT Pipe (12-inch)0 12.000 1.00 0.0 0.0 100%0.0
CT Pipe (2-inch)0 2.00 0.17 0.0 0.0 100%0.0
0.00 0.0 0.0 100%0.0
0.00 0.0 0.0 100%0.0
0.00 0.0 0.0 0.0
0.00 0.0 0.0 0.0
0.00 0.0 0.0 0.0
0.0
Estimate Pipe Disinfection CT
Residual Conc., C
(mg/L) 1 pH 2 Temp. (°C) 3
(See Table B
below)
Peak Flow
(gpm)
Effective
Volume
(gal)
Total
Detention
Time (min)
Contact
Time (T)
(min)
Total Pipe CT
(C*T) 4
2 6-9 0.5 24.0 0.0 0.0 0.0 0.0
Estimate Storage Tank Volume & Disinfection CT
Tank Description
Residual
Conc., C
(mg/L)
pH 2 Temp. (°C) 3
(See Table B
below)
Peak Flow
(gpm)
Baffling
Factor, BF
(See Table A
below)
Minimum
Volume
(gal) (at
lowest setting)
Total Detention
Time, TDT (min)
Contact
Time (T)
(min)
CT (C*T)
Vol/Peak Flow TDT x BF C*T
Mix Master Tank 2 6-9 0.5 24.0 0.6 160 6.7 4.0 8.0
6-9 0.5 1.0 0.0 0.0 0.0
6-9 0.5 1.0 0.0 0.0 0.0
6-9 0.5 1.0 0.0 0.0 0.0
6-9 0.5 1.0 0.0 0.0 0.0
6-9 0.5 1.0 0.0 0.0 0.0
8.0
Summary
6 (See Table B below, assuming worst scenario)
8.0 (= Total Pipe CT + Total Tank CT)
Yes
Notes:
1. Residual conc. is the disinfectant level measured at (or after) the end of the pipe/vessel [NOT the dose added at the beginning of the pipe/vessel].
2. Assuming pH between 6 and 9
3. Assuming water temperature of 0.5 °C in winter worst scenario
4. This tool provides rough estimate of disinfection CT. For detailed design, apply additional safety factor and other design considerations.
Factor
6-9 10
0.5 12 90
5 8 60
10 6 45
15 4 30
20 3 22
25 2 15
Enter only the green field
CT Req'd for 4-Log Virus Inactivation
Perforated inlet baffle, serpentine or
perforated intra-basin baffles, outlet weir or
perforated launders
0.1
Total Pipe Effecive Volume (gallons)
pHTemp (oC)
Total Estimated Disinfection CT 4
Meeting 4-Log Virus Inactivation?
None, agitated basin, very low length to
width ratio, high inlet/outlet velocities
Total Tank CT 4
Penny's Café Water System #23075 File #
Very high L to W ratio (pipeline flow),
perforated inlet, outlet & intra-basin baffles
4- Log Inactivation of VirusesDescription
Table A
Tank Baffling Factors
0.7
1
0.3
0.5
Single or mutliple unbaffled inlets or
outlets, no intra-basin baffles
Baffled inlet/outlet with some intra-basin
baffling
Table B
Free Chlorine CT Values (per EPA, 1991)
DDW-Eng-0031 1 5/13/2016